For your information, I built a private solution that
1) create small olap cubes from Hadoop
2) upload them to mongo
3) use DC.js to visualize them
Of course, the trick is to know which cubes to materialize up front. But that's not a new concept, it is almost the same as aggregated views for olap servers. For those interested by the subject, Avatara (
http://engineering.linkedin.com/olap/avatara-olap-web-scale-analytics-products) is a nice read.
The real problem is to identify where the computation should be done : Hadoop versus Database/server versus Browser. The closest to the end user, the fastest the 'animation' can be but of course the farthest to the end user, the biggest is the amount of data that can be processed/manipulated.
Crossfilter is really only useful to do the computation on the browser.
Bertrand